Today I went out in my back yard to fly my Phantom. I live on a river and was launching out back on my dock. I have done this over 300 times. It was a beautiful day out, and I started up the Phantom just like I normally do, all according to DJI instructions. On my way out to my dock, one of the motors started, turning on one of the props, (I normally turn on the controller, range extender and Phantom while I walk out to the dock). I turned the battery off, which was the only way it would turn off. After a couple minutes I powered it back on and waited for GPS signal. I had 12 satellites. I was attempting to connect my phone to the WIFI, and while I was doing this, all four motors turned on and the Phantom started to lift off the ground. I hadn't even touched the controls yet. It lifted off and immediately darted towards the water and crashed and of course sunk. I didn't have any control while it was doing this.

A couple things I will add:

1). This drone was purchased new by myself. I let my son fly it one day and he crashed it into the river. I sent it to have it fixed, and they fixed it (DJI authorized service center in Miami Florida). I don't know what exactly they did, but it was good as new. At least for a week until this happened. I received it back from service on Saturday, October 11 and it crashed today, October 15. I flew several flights in between receiving it back and the crash today, all without incident.

2). My dock does not have a roof, so there was no interference.

3). The battery was fully charged, as well as fresh batteries in controller and charged wifi extender.

Does anyone have any idea why this would happen? Could it be something that went wrong with service? Was this just a glitch? Should I spend another $1300 on a new one?